Display screen or portion thereof with transitional computer graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with transitional computer graphical user interface according to the claimed design;

FIG. 2 is a second image thereof;

FIG. 3 is a front view of a second embodiment of a display screen or portion thereof with transitional computer graphical user interface according to the claimed design; and,

FIG. 4 is a second image thereof.

The appearance of the transition is sequential from FIG. 1 to FIG. 2 and from FIG. 3 to FIG. 4. The process or period in which an image transitions to another image forms no part of the claimed design.

The grey shading illustrates contrast which is part of the claimed design.

The longer-incremented broken-lines showing a portion of an electronic device and the intermediate-length broken-lines showing a display screen boundary, as well as the still shorter broken-lines illustrating portions of the graphical user interface form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional computer graphical user interface, as shown and described. 